日夜(にちや)

日夜(にちや) emphasizes tireless, continuous effort — working or happening both day and night without pause.

COMPOUND: 日(にち) (day) + 夜(や) (night)

REGISTER:
Somewhat formal and literary. In casual speech, いつも or ずっと would be more natural.

COMMON PATTERNS:

• 日夜(にちや)努力(どりょく)する: to make efforts day and night
• 日夜(にちや)研究(けんきゅう)する: to research day and night
• 日夜(にちや)稼働(かどう)する: to operate around the clock

SIMILAR EXPRESSIONS:

• 昼夜(ちゅうや): day and night (similar meaning, slightly more neutral)
• 四六時中(しろくじちゅう): around the clock, constantly (colloquial)
• 絶(た)えず: constantly, unceasingly (more formal)